In modern trailer vehicles of traction vehicle-trailer combinations, what are referred to as combination cylinders are usually used as brake cylinders, which combination cylinders comprise, on the one hand, a service brake cylinder as an active service brake, which is ventilated in order to apply the brake and vented in order to release the brake, and, on the other hand, a spring brake cylinder as a passive parking brake, which is vented in order to apply the brake and ventilated in order to release the brake.
FIG. 1 shows a park/shunt valve arrangement 1 from the prior art, which park/shunt valve arrangement 1 serves on the one hand, in a trailer vehicle of a traction vehicle-trailer combination, when parking with the trailer still coupled at the coupling head, to vent the spring brake cylinders so that the spring brake is applied (“parking function”). On the other hand, legislators require that the spring brake is applied automatically in the event of tearing off the compressed air supply of the trailer vehicle (“tear-off function”). This function is also integrated into the known park/shunt valve arrangement 1. Last but not least, the tear-off function must also be capable of being deactivated if the trailer is to be maneuvered in the uncoupled state by a vehicle without a compressed air supply. This shunting function is also carried out by the park/shunt valve arrangement 1 in the prior art.
According to the diagram of the prior art park/shunt valve arrangement 1 in FIG. 1, said park/shunt valve arrangement 1 comprises a shunting valve 2 which is assigned to the shunting function, a tear-off valve 4 which is assigned to the tear-off function, and a parking valve 6 which is assigned to the parking function.
The shunting valve 2 is a 3/2 way valve which can be activated by a switch 18 into a first switched position, in which an inlet 10 which is connected by a coupling connection 8 to the “supply” coupling head of the trailer vehicle is closed and an inlet 14 which is connected by a supply connection 12 to a trailer-vehicle-side compressed air supply is connected to an outlet 16, and which 3/2 way valve can be switched pneumatically into a second switched position, in which the inlet 10 which is connected to the coupling connection 8 is switched through to the outlet 16, by the supply pressure which is present at a control inlet 20 and is conducted from the coupling connection 8 via a control line 22. However, the shunting valve 2 can be activated into the first switched position by the switch 18 only if the pressure at the control inlet 20 is lower than a predefined limiting pressure, for example lower than the supply pressure at the coupling connection 8.
The outlet 16 of the shunting valve 2 is connected via a control line 24 to a control inlet 26 of the tear-off valve 4, which is embodied, on the one hand, as a control-pressure-activated 3/2 way valve, and on the other hand, also as a spring-activated 3/2 way valve, and to an inlet 28 of this valve 4. In its first, spring-activated switched position, the tear-off valve 4 closes the inlet 28 and connects its outlet 30 to a further outlet 32 which is connected to a venting connection 34. In its second, pressure-activated switched position, said tear-off valve 4 switches through its inlet 28 to the outlet 30 and closes the further outlet 32 which is connected to the venting connection 34. As long as a sufficient control pressure is present at its control inlet 26, the first spring-activated switched position cannot be assumed.
An inlet 36 of the parking valve 6, which is also embodied as a 3/2 way valve, is connected to the one outlet 30 of the tear-off valve 4. The parking valve 6 is activated in a purely mechanical way, while, when a switch 38 is activated in accordance with a first switched position, the inlet 36 is closed and an outlet 42, which is connected to a shuttle valve connection 40, is connected to a further outlet 44, which is connected to the venting connection 34. In contrast, according to a second switched position which is shown in FIG. 1, the inlet 36 is connected to the outlet 42 which leads to the shuttle valve connection 40 which is connected to the spring brake cylinders of the trailer vehicle. The first and second switched positions of the parking valve 6 can be locked or latched.
Two non-return valves 46, 48 between the outlet 16 of the shunting valve 2 and the inlet 28 of the tear-off valve 4 or said inlet 28 and the one outlet 30 of the tear-off valve 4 ensure that compressed air can flow only in the respectively permitted direction.
FIG. 2 shows a detail of a circuit diagram of a known pressure regulating module 50 which is assigned to the trailer and which interacts with the park/shunt valve arrangement 1 in FIG. 1. The pressure regulating module 50 includes, controlled in a known fashion by an electronic control device 52, a backup valve 54, an inlet valve 56 and an outlet valve 58, which actuate a relay valve 60 which modulates, as a function of a control pressure present at its control inlet 62, a brake pressure at its outlet 66 which is connected to service brake connections 64 for the service brake cylinders, and/or connects these connections 64 to a venting connection 68. The outlet 66 of the relay valve 60 is also connected to an inlet 70 of a shuttle valve 72, the further inlet 74 of which is connected to the shuttle valve connection 40 of the park/shunt valve arrangement 1 in FIG. 1. The shuttle valve 72 transmits the greater pressure of pressures prevailing at its two inlets 70, 74, these being, on the one hand, the service brake pressure modulated by the relay valve 60 and, on the other hand, the supply pressure present at the shuttle valve connection 40, to its outlet 77 which is connected to spring-type connections 78 which lead to the spring brake cylinders. The shuttle valve 72 serves to prevent overloading of the components of the spring brake cylinders by superimposing the supply pressure on the service brake pressure (force limitation).
When the trailer vehicle is coupled in the travel mode, supply pressure which is conducted from the shuttle valve connection 40 of the park/shunt valve arrangement 1 in FIG. 1 via the “supply” coupling head passes to the one inlet 74 of the shuttle valve 72, while the other inlet 70 is supplied with the service brake pressure of the relay valve 60 during the operation of the service brake, which service brake pressure is generally derived from the supply pressure and is therefore lower than said supply pressure. For this reason, the supply pressure which is present at the one inlet 74 of the shuttle valve 72 is usually transmitted to the spring-type connections 78 in order to keep the spring brakes released in the travel mode.
Against this background, the method of functioning is as follows: during operation, i.e. when the traction vehicle-trailer combination is traveling, the valves 2, 4 and 6 are in the switched-through positions shown in FIG. 1, in which the supply pressure which is present at the coupling connection 8 and is conducted from the traction vehicle is transmitted through the valves 2, 4 and 6 to the shuttle valve connection 40. In this context, the supply pressure is present at the control inlet 26 of the tear-off valve 4, and therefore sufficient control pressure is present to hold said tear-off valve 4 in the second switched position counter to the effect of the valve spring, in which second switched position its inlet 28 is switched through to the outlet 30. Since the supply pressure is generally higher than the service brake pressure which is derived therefrom, the supply pressure prevails over the service brake pressure at the shuttle valve 72 and ventilates the spring brake cylinders in order to keep the spring brakes released.
After the traction vehicle-trailer combination has been braked with the active service brake in order to park it, the parking brake can be applied with the trailer still coupled to the traction vehicle (“parking function”). To do this, the driver of the vehicle activates the switch 38 and moves the parking valve 6 from the second switched position shown in FIG. 1 into the first switched position in which it connects the shuttle valve connection 40 to the venting connection 34, while its inlet 36 is closed. Compressed air therefore flows from the spring brake cylinders via the spring-type connections 78, the shuttle valve 72, the shuttle valve connection 40 and the venting connection 34 into the open air, as a result of which the spring brake cylinders are vented and the spring brakes are applied for parking. At the same time, the closed inlet 36 prevents the supply pressure which is present at the coupling connection 8 from being able to flow out.
If, on the other hand, the trailer vehicle which is being braked to a stationary state by the service brake is decoupled from the traction vehicle without activation of the parking valve 6, the pressure at the coupling connection 8 drops rapidly, as it also does at the control connection 26 of the tear-off valve 4, as a result of which the latter switches over under spring activation from the second switched position (shown in FIG. 1), in to the first switched position in which its outlet 30, which is switched through to the shuttle valve connection 40 via the parking valve 6, is connected to the venting connection 34, as a result of which the spring brake cylinders are automatically vented and the spring brakes are applied. In contrast, the inlet 28 of the tear-off valve 4 is closed, with the result that compressed air cannot flow out from the supply connection 12. The described sequence occurs even when the hose connection is torn off or a leak occurs in the hose connection between the “supply” coupling head of the traction vehicle and the “supply” coupling head of the trailer, because the pressure at the coupling connection 8 then also drops rapidly (tear-off function).
If leakage or tearing off therefore occurs in the hose connection between the traction vehicle and the trailer, the pressure at the “supply” coupling head, at the coupling connection 8 and at the control connection 26 of the tear-off valve 4 therefore decreases rapidly, as a result of which said tear-off valve 4 switches over under spring activation from the second switched position shown in FIG. 1 into the first switched position in which its outlet 30 which is switched through to the shuttle valve connection 40 is connected to the venting connection 34, with the result that the pressure at the shuttle valve connection 40 and therefore also at the inlet 74 of the shuttle valve 72 also drops.
If the driver does not brake with the service brake, the pressure at the other inlet 70 of the shuttle valve is also low, with the result that the overall low pressure at the outlet 76 of the shuttle valve leads to automatic application of the spring-loaded cylinders. However, if the driver brakes, the shuttle valve 72 switches through the now higher brake pressure at its outlet 76 and conducts it to the spring brake cylinders, for which reason the spring brake is released. However, at the same time, the service brake pressure is also present at the service brake connections 64, as a result of which the service brake is applied, with the result that the requirement for braking of the trailer vehicle after a leak or tearing off of a hose is met. If the brake pressure is low enough for the spring brakes to be able to be applied, the braking force is composed of the braking force of the service brake and the braking force of the spring brake, as a result of which the condition of braking of the trailer vehicle in the case of leakage or tearing off of a hose is again met.
If it is desirable to move or to maneuver the parked trailer vehicle, braked by the spring brakes, by a vehicle without a compressed air supply, for example by a fork lift truck (shunting function), the spring brake must be released. To do this, an operator activates the switch 18 of the shunting valve 2, as a result of which the supply connection 12 which is connected to the compressed air supply which is connected to the trailer is switched through to the shuttle valve connection 40 via the switched-through tear-off valve 4 and the switched-through parking valve 6. As a result, the spring brake cylinders are ventilated and therefore the spring brakes are released.
Generally, at least the following functions are therefore, carried out by a valve arrangement for controlling a brake system, comprising at least one spring brake cylinder and at least one service brake cylinder, of a trailer vehicle of a traction vehicle-trailer combination:                a) a first function (tear-off function) according to which the trailer vehicle is braked if there is an interrupted or disrupted compressed air connection between the traction vehicle and the trailer vehicle,        b) a second function (shunting function) according to which the spring brake is released as a function of an external signal by the supply pressure of a trailer-vehicle-side compressed air supply when there is an interrupted compressed air connection between the traction vehicle and the trailer vehicle,        c) a third function (parking function) according to which the spring brake is applied as a function of a further external signal when the trailer vehicle is coupled, and        d) a fourth function according to which either a service brake pressure which is modulated for the service brake by a control valve device or a supply pressure is transmitted to the spring brake in order to release the latter or keep it released.        
In contrast, the exemplary embodiments and/or exemplary methods of the present invention is based on the object of developing a valve arrangement of the type mentioned at the beginning in such a way that the functions specified above are carried out with as little expenditure as possible or by using as few valves or components as possible, in order to obtain a valve arrangement which is more cost-effective and simpler in design.